In the art of making tires, it is desirable to employ rubber vulcanizates that demonstrate improved rolling resistance, wet skid resistance, and reduced hysteresis loss, at certain temperatures. Factors believed to affect these properties include the degree of filler networking (particle agglomeration), the degree of polymer-filler interaction, the cross-link density of the rubber, and polymer free-ends within the cross-linked rubber network.
Inorganic fillers, such as silica, impart improved wet traction and improved snow traction when used as filler within tire treads. Mixing silica into a tire stock, however, is difficult because silica particles agglomerate and therefore they are not easily dispersed. In response, processing and dispersing aids are used during compounding. Unfortunately, the use of these processing and dispersing aids may enhance the decrease in modulus at high temperatures. In addition, silica particles are less compatible than carbon black with rubber molecules.
Because precipitated silica has been increasingly used as reinforcing particulate filler in tires, there is a need to overcome the processing problems associated with silica fillers. Additionally, there is a need to increase polymer-filler interaction in silica-filled tires, thereby improving rolling resistance, abrasion, and wet skid resistance.